Electron tube design



y 6, 1964 H. A. WHITE 3,134,922

ELECTRON TUBE DESIGN Filed March 25, 1962 INVENTQR. Hugh 4. wh/fe F T E Ei 0% 477'0RN5X5.

r 3,134,922 Ice Patented May 26, 1964 3,134,922 ELECTRON TUBE DESIGN Hugh A. White, 3981 Chilton Lane, San Bruno, Calif. Filed Mar. 23, 1962, Ser. No. 182,006 Claims. (Cl. 313-268) This invention relates to an electron tube design and more particularly to tubes of the nested electrode type.

In prior art electron tube designs the various tube elements that is, the cathode, grid and anode, are supported in a concentric fashion by means of mica discs. Not only are these mica discs somewhat fragile but the support between the various elements constitutes a relatively short path between the elements themselves.

In the normal use of the tube, especially at high temperatures, the cathode material tends to sublimate on the surfaces within the tube. These surfaces almost always include the mica insulating and spacing discs. Although the sublimation on the mica disc constitutes a relatively high resistance, the resistance creates problems as the tube components contract and expand in normal use. Consequently, then, even though the sublimation resistance between the cathode and grid may be in the order of ten megohms, considerable noise is produced.

It is, therefore, a general object of this invention to provide an improved electron tube' design.

It is a more particular object of this invention to provide an electron tube design wherein the spacing elements for the various electrodes of the tube constitute relatively long paths between the electrodes themselves.

It is a more particular object of this invention to provide an electron tube having the aforementioned characteristics wherein the effects of sublimation are reduced without the necessity of cooling individual portions of the electrode such as by conducting heat from a cathode to a heat sink or the like.

These and other objects and features of the invention will become more clearly apparent upon a review of the following description in conjunction with the accompanying drawing, in which:

FIGURE 1 is an elevational view with part of the envelope broken away, of an electron tube in accordance with one embodiment of this invention;

FIGURE 2 is an exploded view of the tube shown in FIGURE 1 wherein the electrode construction is depicted;

FIGURE 3 is an axial cross sectional view of an electrode assembly of the tube shown in FIGURE 1 and taken along the line 33 of FIGURE 2; and

FIGURES 4, 5 and 6 are plan views of insulating discs as employed in the tube shown in FIGURE 1.

Referring to the drawings, in which identical elements bear like reference numerals, there is included an envelope 11 in which an electrode assembly 13 is disposed. A plurality of pins 15 extend through the bottom of the envelope 11 in the usual manner for connection to the various electrodes.

The tube includes a cathode 17, a grid 19 and an anode 21. As can better be seen in FIGURE 3 the cathode includes a conductive tube 23 having a coating of electron emissive material 25 on the exterior thereof. An insulating coating 27 is formed on the interior of the cathode tube 23 and a conventional filament 29 is fitted within the cathode against the insulating coating 27. The filament leads 31 are connected to pins 33.

As can be clearly seen in FIGURE 2, the cathode 17 is nested within the grid 19 while the grid is nested within the plate 21. Moreover, the length of the various electrodes is graduated such that the centermost, that is the cathode 17, is the longest while the grid 19 and plate 21 are respectively shorter.

In order to secure each of the electrodes in a fixed space relationship a plurality of ceramic insulator discs 35 to 40 are employed. The discs 35 and 40 may be considered as cathode supporting discs; the discs 36 and 39 as grid supporting discs and the discs 37 and 38 as anode supporting discs. Each of the discs includes an opening for receiving its respective electrode. Thus, the discs 35 and 40 include a central opening 43 having a dimension corresponding to the outside dimension of the cathode 17. Likewise the grid discs 36 and 39 have an opening 45 corresponding to the dimension of the grid 19 and the anode discs 37 and 38 have an opening 47 corresponding to the outside dimension of the anode 21.

Each end of the various electrodes are fitted into the respective supporting discs and secured thereto by conventional means such as by a force fit or by peening.

In order to retain the discs themselves in spaced relationship a plurality of spacers 49 are employed. The spacers are chosen such that their cross section taken along the line x-x of FIGURE 3 in a direction transverse to their extension from one disc to another has an outer perimeter substantially less than the length of the path interconnecting each spacer on the disc as shown for in stance, by the dashed line path 51 in FIGURE 4. Thus, in referring to FIGURE 3, a leakage path from one electrode to the next, for instance from the cathode 17 to the grid 19, includes the radius of the cathode support washer 35 or 40, the length of the spacer 49 having a relatively narrow path width, and the radius of the grid support disc 36 or 39. Consequently, even in the event of sublimation the leakage path is relatively long and includes a narrow restriction as defined by the spacers 49.

In addition to the spacers 49 there may also be included spacers 53 which extend from the support discs at one end of the electrodes to the support discs at the other end thereof. Thus, with the spacers 53 the rigidity of the electrodes itself is not relied upon in order to provide rigidity to the overall electrode assembly.

In order to provide connection from the outside of the electron tube to the various electrodes therein the insulating discs 35 to 40 are each supplied with strips of conductive material. Thus, on the cathode support discs 35 and 40 conductive strips 55 are included. Conductive strips 57 and 59 are included on the grid and anode support discs respectively. In each case the conductive strips 55, 57 and 59 communicate from the electrode receiving opening within the disc to the perimeter thereof. Thus, the strips may be conveniently plated on the ceramic support discs such that the interior of the openings 43, 45 and 47 are plated as well as the strips 55, 57 and 59. Thus, good electrical contact is made to each electrode to the perimeter of the respective support discs.

A terminal 61 is located on the cathode support disc in communication with the conductive strip 55. Thus, a connecting rod 67 may communicate from the terminals 61 to the cathode pin 69. Likewise, conductive rods 71 and 73 may communicate from their respective terminals 63 and 65 to the grid and anode pins and 77.

Thus, it is seen that the connections to the various electrodes may be made on the perimeter of the insulating discs 35 to 40 creating a wide separation for the various rods 67, 71 and 73 whereby interelectrode capacity to the tubes is substantially reduced and higher frequency operation is feasible.

Variations on the connection of the electrodes to the exterior of the tube may include the extension of the rods 67 and 71 and 73 toward each end of the tube envelope 1]. whereby a set of pins 15 may be mounted at each end of the tube. Moreover, if desired the rods 67, 71 and 73 may be connected to only one insulator disc for each of the electrodes. Thus, the rod 67 may extend only to the disc 40 with the rods 71 and 73 extending only to the discs 39 and 38 respectively. Alternatively, the rods may be arranged in two sets whereby one set connects the lower insulated discs 38, 39 and 40 to a set of pins at the bottom of the tube while the other set connects the discs 35, 36 and 37 to a set of pins at the top of the tube.

In addition to the conductive strips shown, various circuit elements such as resistance, capacitance or inductance, may be imprinted or plated on the insulator discs to provide within the tube itself functions which are usually performed outside the tube.

In order to facilitate fabrication, each of the insulator discs 35 to 40 may include a notch 79 to simplify alignment in a jig.

Thus, it is seen that an improved electron tube design is provided which includes a substantially long sublimation path between electrodes thereby permitting a higher temperature of operation. In addition, connection to the exterior of the tube may be conveniently made at each end of the envelope. Moreover, the external connection to the electrode may be made near the perimeter of a relatively large diameter insulated disc whereby interelectrode capacitance is substantially reduced. It is apparent, therefore, that the manufacture of relatively complex tubes may be substantially simplified.

The use of ceramic insulator discs rather than the usual mica discs provides, in addition to the increased strength, improved operation characteristics due to the non-gasing nature of ceramics. Moreover, the use of ceramics simplifies the manufacture of conductive strips such as the strips 55, 57 and 59 which may be simple and conveniently plated on the ceramic. The paths between electrodes are relatively long whereby interelectrode resistance due to sublimation is reduced. This is accomplished without the requirement of conducting heat away from the electrodes, such as by the use of relatively heavy conductors between the cathode element and the pins of the tube.

I claim:

1. In an electron tube, a plurality of electrodes nested one within the other, the length of the electrodes being graduated with the centermost electrode being the longest, means for securing said electrodes in fixed spaced relationship, said means comprising a separate insulator disc at each end of each electrode, each of said discs having an opening therein corresponding to the outside dimension of its respective electrode, said electrodes being held within said openings, and means for retaining said discs in spaced relationship.

2. An electron tube as defined in claim 1 wherein said insulator discs comprise ceramic wafers.

3. An electron tube as defined in claim 1 together with a conductive strip communicating from the opening to the outer periphery of at least one of the discs associated with each electrode whereby connection to the various electrodes may be made at the perimeter of the discs.

4. An electron tube as defined in claim 1 wherein the means for retaining said discs in spaced relationship comprises spacers located between said discs.

5. An electron tube as defined in claim 4 wherein said spacers are insulators, the cross section of said spacers in the direction transverse to their extension from one disc to another having an outer perimeter substantially less than the length of a path interconnecting each spacer on said disc, whereby the Width of a leakage path from one electrode to the next is substantially reduced.

No references cited. 

1. IN AN ELECTRON TUBE, A PLURALITY OF ELECTRODES NESTED ONE WITHIN THE OTHER, THE LENGTH OF THE ELECTRODES BEING GRADUATED WITH THE CENTERMOST ELECTRODE BEING THE LONGEST, MEANS FOR SECURING SAID ELECTRODES IN FIXED SPACED RELATIONSHIP, SAID MEANS COMPRISING A SEPARATE INSULATOR DISC AT EACH END OF EACH ELECTRODE, EACH OF SAID DISCS HAVING AN OPENING THEREIN CORRESPONDING TO THE OUTSIDE DIMENSION OF ITS RESPECTIVE ELECTRODE, SAID ELECTRODES BEING HELD WITHIN SAID OPENINGS, AND MEANS FOR RETAINING SAID DISCS IN SPACED RELATIONSHIP. 